Grounding clamp and connector for abutting wire ducts



May 17, 1960 E. w. SELNAU CRCUNDINC CLAMP AND CONNECTOR FCR ABUTTINCWIRE DuCTs Filed June 14, 1957 Elmer W. Selnou United States Patent O"GROUNDING CLAMP AND CONNECTOR FOR ABU'ITING WIRE DUCTS Elmer W. Selnau,Bristol, Conn., assigner to The Wiremold Company, West Hartford, Conn.,a corporation of Connecticut Application June 14, 1957, Serial No.665,701 11 claims. (cl. 114-84) This invention relates to means forconnecting together adjacent sections of metal electric wire ductsorraceways firmly and, at the same time, making a good electricalconnection between these sections to provide a continuousv groundconnection.

The invention is applicable to duct sections which are inv alignment orcome together at right angles or otherwise.

Metal electrical wiring ducts for continuous insulated electricconductors or wires are commonly formed of a back or base strip overwhich a cover strip lies and in many cases interlocks as the cover andbase strip are pressed or snapped into engagement. Customarily the ductsare grounded. When one section abuts another, the problem is to providea good continuous ground connection between the two at the same timethat the sections are physically connected together.

Thus, one object of the invention is to provide a good rm permanentelectrical and mechanical connection which can be economicallyfabricated and easily applied with a minimum amount of labor.

Another object is to provide a sheet metal clamping device forconnecting together adjacent metal wiring duct sections Vwhich can beput in place easily at the desired location and permanently secured bymerely tightenining two screws.

Another object is to create a connecting device of the aforementionedtype on principles which are applicable to connectorsY for aligned orfor angular abutments of wiring duct sections.

Otherl objects and advantages of the invention will appear as it isdescribed in connection with the accompanying drawings.

In the drawings:

Fig. 1 is a plan View, partly broken away, of the invention 'as appliedin connecting aligned abutting sections.

Fig. 2 is a transverse section view on line 2--2 of Fig. 1 with theconnecting device loosely placed in position. .l

Fig. 3 is a view similar to Fig. 2 with the securing screw tightened to'secure the clamp and connector for permanent connecting condition.

Fig. 4 is a perspective view, partly broken away, of the invention asapplied to duct sections abutting at right angles. 1

Referring to the drawings, the invention is shown as applied to electricwiring ducts of the sort shown in Patent No. 2,743,423 of W. E. Parks,issued April 24, 1956. Such ducts have a base strip in the form of achannel having a flat back wall and parallel side walls 12 and lfbentvup at right angles to the back walls with their edges bent obliquelyinward, forming lips 12', 14. A sheet metal cover member (not shown) isalso in channel form and has its edges shaped to interlock with the lipsof the base as described in said patent.

1t will be understood, however, as the invention is described, that theinvention is not limited to the form ICC of duct or raceway mentionedand illustrated, but is applicable to'various other forms of ducts.

For connecting ducts A and B in alignment, a connecting and clampsupporting plate, designated generally by the numeral 20, is stampedfrom sheet metal with two spaced raised bosses 22 in the longitudinalcenter line of the plate. Each boss is pierced and tapped for thereception of securing bolts 24, 25. Over each boss is placed a bowedclamping strip 30, 32 of stili spring metal harder than the ductmaterial. Portions 30a.and 32a adjacent the ends of these clampingstrips are bent to lie parallel to the back wall 10 of the duct when thestrips are loosely spaced in position, as shown in Fig. 2;

but the extreme edge portions 30e and 32e are bent to' point intocorners of the raceway when the strip isrput in place (see Fig. 2) andare serrated to provide teeth for biting into the side walls 12 and 14of the duct.

To support the clamping strip on a fulcrum edge at the joint between theat portion 30a and the bent down serrated edge portion 30e (or 32a and32e), the edge portion 28 of the connecting and clamp supporting plate20 is bent up at an oblique angle (30 to the horizontal approximately)and is cut away, for a distance slightly greater than the width of theclamping strip, providingv notches 28nthrough which the clamping stripsextend.

As the screws 24, 25 are tightened onto the clamping strips 30 and 32,the bow or arch of the clamping strip attens due to pressure of theunderside of the screwhead on the surface of the clamp, as shown in Fig.3. During this flattening, the longitudinal edges of the notches 28 actas fulcrums about which pivot the portions of the strip on either sideof the screw. This pivoting, together with the elongation of theclamping strip due to its flattening, causes the teeth to bite into andscrape over the inside surface of Vthe side walls 12 and 14 of the ductas the teeth and edge travel in a curved path from the bottom upwardly;

The clamping strip is firmly secured to the duct by the wedging andbiting action of the clamping. strip, which at the same time by itsteeth scraping the metal of the ducts and biting into it, alfords a goodelectrical connection between the clamping strip and the duct.

yBy placing a connecting plate so that one half lies in one duct sectionand theother half lies in the second section abutting the iirst, the twosections can be connected and secured togetheL Thus, the clamping stripsare secured to the plate 20 by the screws 24, 25 both electrically andphysically, and the plate is joined to the adjoining sections by reasonof the engagement rof the clamps with the side walls of the ducts.

The clamping strips 30, 32 are preferably formed so that when in theunstressed condition as illustrated in Fig. 2, their overall length isslightly less than the distance between the inside surfaces of theparallel side walls 12 and 14 of the duct. Similarly, the width of theconnecting and supporting plate 20 is made so that its overall dimensionis less than the distance between said sidewalls.

To add transverse stiffness to the plate 20 and prevent buckling anddistortion, three or more spaced transverse ribs may be pressed into theplate adjacent the ends and middle of the plate, respectively.

When. it is desired to connect two ducts C and D together at rightangles, the connecting and supporting plate which is made longer thanbefore is bent transversely of its length at its mid-line, at a rightangle, as illustrated in Fig. 4. In this form of the invention, theclamping strips and 132 are the same as clamping strips 30 and 32 inFigs. 1-3 and they cooperate with the two ends or arms of the connectingand supporting plate 120 in the same way as before.

Inv order to guide the wires around the bend and prevent their gettingcaught or pinched within the duct when the cover is applied, a pair ofguide fingers 127, 129 are formed on each arm of the connecting andsupporting plate'120 located between the bend of the plate and theclamping strips 130 and 132, respectively. These guide lingers' limitlateral movement of the wires to a predetermined area to achieve thedesired end.

At the midpoint lengthwise of the connecting and supporting plate 120where the angle bend is, an oblong opening may' be formed in one arm forthe passage of conductor wires (not shown), if it is desired to havethem continue through into an injunction aligned strip or for any otherreason. The end of the duct is otherwise closed by the bent up leg ofthe connecting and supporting member 1,20. The opening 123 may beprovided as a knockout to be removed only when an opening isneeded.

Stitfening ribs 121 are provided in the connecting and supporting plate120 as in the form of invention illustrated in Figs. 1-3 near to andparalleling the clamping members 130, 132.

Many modications of the invention will occur to those skilled in theart. Therefore, the invention is not limited to the specific formsillustrated and described.

' What is claimed is:

1. A connection for connecting abutting channel-shaped electric wiringduct sections having side and back walls comprising plate means withinthe duct sections adapted to be seated partly on the back wall of onesection and partly on the back wall of an abutting section, clampingmeans within the duct sections engaging the portions of said plate meanslying in each of said two abutting sections, means passing freelythrough said clamping means and drawing said plate means and clampingmeans toward each other and also securing them to said two sections andsecuring said sections together electrically and mechanically.

2. A connection for connecting abutting channel-shaped electric wiringduct sections having side and back walls comprising plate means withinthe duct sections adapted tobe seated partly on the back wall of onesection and partly on the back wall of an abutting section, clampingmeans in each section overlying said plate means, means to secure saidclamping means to said plate means, said securing means acting on saidclamping means to cause the latter to bite into and make cleanelectrical connection with said'duct sections.

3. A connection for connecting abutting channel-shaped electric wiringduct sections comprising plate means within the duct sections adapted tobe seated partly on the backiwall of one section and partly on the backwall of an abutting section, bowed resilient clamping means within theduct sections overlying the parts of said plate means which lie in eachsection, means to secure said clamping means to said plate means andflattening the bowed portion to elongate it into clamping engagementwith the side walls of the ducts.

4. A connection as claimed in claim 3 having means on the end of saidclamping means for biting into said duct walls as the clamping meansflattens.

5. A connection for connecting abutting channel-shaped electric wiringduct sections having side and back walls comprising plate means withinthe duct sections adapted to be seated partly on the back wall of onesection and partly on the back wall of an abutting section, clampingmeans within the duct sections engaging the portions of said plate meanslying in each of said two abutting sections', means 'to secure s'aidclamping means to said platev meansand also toV said two sections'tosecureand-to electrically connect said sections together, and means onsaid plate means which provides fulcrum points for said clamping means,whereby when said securing means acts on said clamping means the lattermoves over and bites into the duct walls.

6. A connection for connecting abutting channel-shaped electric wiringduct sections having side and back walls comprising plate means withinthe duct sections adapted to be seated partly on the back' Wall of onesection and partly on the back wall of an abutting section, clampingmeans within the duct sections engaging the portions of said plate meanslying in each of said two abutting sections, means to secure saidclamping means to said plate means and also to said two sections tosecure and to electrically connect said sections together, the edges ofsaid plate means being bent away from the back wall of said ductsproviding fulcrums on which said clamping means rests and pivots as saidsecuring means moves said clamping means, whereby the clamping meansscrapes over and bites into the duct walls.

7. A connection for connecting abutting channel-shaped electric wiringduct sections having side and back walls comprising plate means withinthe duct sections adapted to be seated partly on the back wall of onesection and partly on the back wall of an abutting section, bowedclamping means within the duct sections engaging the portions of saidplate means lying in each of said two abutting sections, means to securesaid clamping means to said plate means and also to said two sections tosecure and to electrically' connect said sections together, saidsecuring means engaging and flattening said clamping means andelongating it into engagement with said duct walls, and fulcrum meanscausing said clamping means to move arcuately over the duct walls and tobite into said walls.

8. A connection as claimed in claim 7 wherein the fulcrum means isprovided by bending the edge portions of said plate means away from theback wall of said duct.

9. A connection for connecting abutting channel-shaped electric wiringduct sections having side and back walls comprising plate means withinthe duct sections adapted to be seated partly on the back wall of onesection and partly on the back wall of an abutting section, clampingmeans within the duct sections engaging the portions of said plate meanslying in each of said two abutting sections, means to secure saidclamping means to said plate means and also to said two sections tosecure and to electrically connect said sections together, said platemeans being bent to join duct sections abutting at an angle.

10. A connection as claimed in claim 9 wherein the plate section closesthe joint between the abutting duct sections.

11. A connection as claimed in claim 3 in which the clamping means haveserrated ends which are directed, when unstressed, toward the cornersformed by intersecting side and back duct walls.

References Cited in the tile of this patent UNITED STATES PATENTS821,876 Lauth May 29, 1906 2,197,737 Appleton f Apr. 16, 1940 2,657,823Skinner Nov. 3, 1953 FOREIGN PATENTS 660,919 Great Britain Nov. 14, 1951830,273 Germany 1.. Feb. 4, 1952 1,132,660 `France Oct. 4, 1955

